Buprenorphine hydrochloride and products containing it are effective treatments of opiate addiction. Methods of synthesizing buprenorphine have been known from the late 1960s. For instance, buprenorphine may be synthesized by an alkylation reaction from norbuprenorphine utilizing bromomethylcyclopropane. The bromomethylcyclopropane typically contains an alkenyl impurity which can also participate in the alkylation reaction. This leads to the formation of Impurity A, otherwise known as (2S)-2-[17-(but-3-enyl)-4,5α-epoxy-3-hydroxy-6-methoxy-6α,14-ethano-14α-morphinan-7α-yl]-3,3-dimethylbutan-2-ol. Impurity A is difficult to remove from the final buprenorphine product by known purification techniques, resulting in products with higher impurities than acceptable by the currently prescribed guidelines established by the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) and the United States Pharmacopeial Convention (USP). In addition, the typical synthesis uses preparatory chromatography to purify the crude buprenorphine product, which can be costly and labor intensive. Consequently, there is a need in the art for an efficient process for producing buprenorphine with impurity levels that meet or exceed the ICH requirements.